public class Square
{

    public void Run()
    {
        Console.WriteLine("请输入一个数（开方）");
        var input = Console.ReadLine();
        double x = double.Parse(input);
        double a = 0;
        while (a * a < x)
        {
            if ((a + 1) * (a + 1) >= x)
            {
                break;
            }
            a++;
        }
        while (a * a < x)
        {
            if ((a + 0.1) * (a + 0.1) >= x)
            {
                break;
            }
            a = a + 0.1;
        }
        while (a * a < x)
        {
            if ((a + 0.01) * (a + 0.01) >= x)
            {
                break;
            }
            a = a + 0.01;
        }
        while (a * a < x)
        {
            if ((a + 0.001) * (a + 0.001) >= x)
            {
                break;
            }
            a = a + 0.001;
        }
        var message = $"{a:f3}";
        Console.WriteLine(message);
    }
}